1. Field of the Invention
The present invention relates to a coordinate input apparatus which specifies a coordinate component (a position coordinate) of a selected position on the basis of a change in capacitance, and a display unit including such a coordinate input apparatus.
2. Description of the Related Art
Techniques of inputting a coordinate component (a position coordinate) of a position selected through the use of the screen of a display unit have been known previously. A typical technique among them is a display unit having a touch panel function. The display unit has a structure in which a touch panel sheet is arranged on a display panel, and a position coordinate of an object which comes into contact with the touch panel sheet (a touch object) is specified and inputted through the use of the touch panel sheet.
There are various types of coordinate input apparatuses using such a touch panel sheet, and a widely used coordinate input apparatus is of a type which detects capacitance. In the coordinate input apparatus, the touch panel sheet detects capacitance, and the position coordinate of the touch object is specified and inputted through the use of a change in capacitance.
For example, in Japanese Unexamined Patent Application Publication No. 2000-76014, as shown in a top view in FIG. 1A and a sectional view taken along a arrow line B-B of FIG. 1A in FIG. 1B, a touch panel sheet 100 with a structure in which a conductive layer 102 and an insulating protective layer 107 are uniformly formed on an insulating substrate 101, and electrodes 103A through 103D are formed at four corners on the conductive layer 102 is disclosed.
Moreover, in Japanese Unexamined Patent Application Publication No. 2002-108553, as shown in a top view in FIG. 2, a touch panel sheet 200 with a structure in which an insulating layer 204 and an insulating protective layer 207 are uniformly formed on an insulating substrate 201, and a strip-shaped conductive layer 202 extending in an x-axis direction and a strip-shaped conductive layer 205 extending in a y-axis direction are formed with the insulating layer 204 in between, and electrodes 203 and 206 are formed on the conductive layers 202 and 205, respectively is disclosed.